Potatoes do not like the tropical conditions that we have in Thailand. However you could still grow them in the period December to February when temperatures are at its lowest, but even then you will see that they are very susceptible diseases, mainly fungus. The potatoes that you can buy at the supermarkets are not really suitable for using as seed but they will grow. Their yield potential is just lower because of virus infections (not harmful for humans though). Planting them at the end of April is a waste of your time.